Lateral strain in InGaAsSb epitaxial layers grown by LPE: Effect on structural and optical properties

In(0.145)Ga(0.855)As(y)Sb(1-y) epilayers were grown on GaSb(100) substrates by liquid phase epitaxy. Lattice mismatch was analyzed for different As concentrations (y) by high-resolution X ray diffraction (HR-XRD). Epilayers with 0.120 < y < 0.124 showed a positive lattice mismatch, leading to compresive strain. These samples present high crystalline quality and flat surfaces as measured by HR-XRD and atomic force microscopy (AFM). For InGaAsSb layers with As concentrations in the range 0.133 < y < 0.141 a negative lattice mismatch was observed, resulting in tensile strain. Structural defects in these InGaAsSb quaternary layers were clearly shown on the HR-XRD and on the AFM micrographs. Raman spectroscopy measurements on these layers also revealed that lateral strain has a direct impact on the intensities of the LO-like, phonon-plasmon, and disorder-activated LA modes. For all the In(0.145)Ga(0.855)As(y)Sb(1-y) epilayers, the photoluminescence (PL) spectra showed a bound exciton (BE) transition around 635 meV for layers under compresive strain, and BE transition around 637 meV for layers under tensile strain, with additional features observed in samples under tensile strain like donor-to-acceptor pair (DAP) recombination and defect-related emission bands. This study provides new insights into the effect of lateral strain on the crystalline and surface quality, and its effect on the optical properties of the quaternary alloys, which are relevant for novel optoelectronic applications.